I've talked to the pedi yesterday, since I'm giving DD EBM, the rice cereal will thicken up the EBM so that DD is able to keep it down. I actually do notice a difference today when I don't add the rice cereal, DD's spit ups more often and larger volumes than without the rice cereal. If, DD wasn't on EBM, then we'd be giving her the Enfamil AR which is a milk-based formula with rice cereal.
The Zantac that DD is taking is to help soothe her throat/esphogus when she spits up and reduce the amount of acid that the stomache produces.
I've started to stretche out DD's feedings to 4 hours now and she has been able to finish the entire bottle now.